<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
        //灯的状态
        var Light = function() {
            this.state = 'off';
            this.button = null;
        }
        Light.prototype.init = function() {
            var button = document.createElement('button');
            button.innerHTML = '开关';
            this.button = document.body.appendChild(button);
            this.button.addEventListener('click', () => {
                this.buttonWasPressed();
            })
        }
        Light.prototype.buttonWasPressed = function() {
            if (this.state == 'off') {
                this.state = 'on';
                console.log('灯开了');
            }else{
                this.state = 'off';
                console.log('灯关了')
            }
        }
        var light = new Light();
        light.init();
    </script>
</body>
</html>